Rotary compressor

ABSTRACT

A rotary gas compressor of the sliding vane type having a rotor positioned eccentrically within a working chamber provided by a cylinder in the stator housing which is closed by end plates secured to the housing. The rotor carries blades or vanes slidable within slots formed in the rotor to engage the cylinder and sweep the working chamber to compress gas introduced therein. The end plates are formed with arcuate, gas discharge slots connecting the outlet port of the housing with circumferentiallyspaced discharge slots in the rotor in a manner to provide an alternate, low resistance path for gas flow at a point located a substantial distance from the outlet port. This arrangement is effective to reduce the extremely high pressure which is normally generated in the discharge zone as the vanes approach the main outlet port and valve assembly.

United States Patent [191 Newton [451 Aug. 19, 1975 [73] Assignee:Borg-Warner Corporation, Chicago,

Filed: Feb. 4, 1974 Appl. No.: 439,512

Related U.S. Application Data [63] Continuation-in-part of Ser. No.261,846, June 12,

1972 abandoned.

Primary E.\'aminerC. J. Husar Assistant ExaminerLeonard Smith Attorney,Agent, or F irm-Thomas B. Hunter 1 5 7 ABSTRACT A rotary gas compressorof the sliding vane type having a rotor positioned eccentrically withina working chamber provided by a cylinder in the stator housing which isclosed by end plates secured to the housing. The rotor carries blades orvanes slidable within slots formed in the rotor to engage the cylinderand sweep the working chamber to compress gas introduced therein. Theend plates are formed with arcuate, gas discharge slots connecting theoutlet port of the housing with circumferentially-spaced discharge slotsin the rotor in a manner to provide an alternate, low resistance pathfor gas flow at a point located a substantial distance from the outletport. This arrangement is effective to reduce the extremely highpressure which is normally generated in the discharge zone as the vanesapproach the main outlet port and valve assembly.

1 Claim, 4 Drawing Figures PATENTEU AUG 1 9197s M s I m. M. g

ROTARY COMPRESSOR CROSS-REFERENCE TO RELATED APPLICATION Thisapplication is a continuation-in-part of my copcnding application Ser.No. 261,846, filed June 12, 1972, now abandoned.

BACKGROUND AND SUMMARY OF THE INVENTION This invention relates to gascompressors and more particularly to gas discharge arrangements forcompressors.

One common type of rotary gas compressor comprises a bladed or vanedrotor eccentrically mounted in a cylindrical stator housing to provide acrescentshaped working chamber between the rotor and housing. Thechamber communicates with an inlet or suction port and an outlet ordischarge port. During rotation of the rotor, gas flows through thesuction port and into the chamber and is then compressed by the vanesbetween the converging walls of the rotor and the cylinder. As theblades approach the discharge port, the distance between the cylinderwall and the rotor surface is very small; and, as a result, gas is underextremely high pressure in the zone adjacent to the discharge port. Whenthe compressor is operating with high discharge pressure, thisrestriction adjacent the discharge port becomes even more troublesome,resulting in extreme overcompression of the gas and concommitant loss ofefficiency.

There are numerous examples in the prior art of discharge arrangementswhich provide a continuous flow path for discharge gas after suction isclosed. In US. Pat. No. 1,949,723 (Kotelevtseff) issued Mar. 6, 1934, arotor sweeps the compression chamber in such a way that discharge gas iscontinuously directed through a passage in one end wall during the final90 of rotation. Such a device is mechanically fixed as to discharge andprovides only a single path for discharge gas flow.

In US. Pat. No. 2,674,953 (Conde), issued Apr. 13, 1954, the compressionchamber is defined in part by an end wall having an elongated, arcuatedischarge port formed therein. This has the disadvantage that the gas,which is in the final stage of compression before the vane passes intothe area of the port, will blow-back (short circuit) into the pocketdefined between the leading and trailing vanes. This could cause aserious loss in capacity, because it would perform a considerable partof its work forcing the gas from a leading pocket to a trailing pocket.

The rotary gas compressor of the present invention is characterized bythe provision of an improved gas discharge arrangement featuring ahousing having a discharge port, which is covered by a discharge valve,and arcuate slots in its end faces communicating with said outlet portand cooperating with fluid passages in the rotor adjacent each vane toprovide a secondary, low pressure drop path for gas flow at a pointlocated at a substantial distance from the outlet port in the housing.In this arrangement, the gas may begin to flow to the outlet port assoon as the rotor ports are in communication with the distal ends of theslots in the housing, provided there is sufficient pressure to overcomethe opening force on the discharge valve. This alternate. low resistancepath is effective in reducing the extremely high pressures otherwisenormally generated in the discharge zone of a conventional gascompressor as the vanes approach the discharge port.

Another aspect of the invention relates to the location of the arcuateslots in the end faces. Except for the outlet end of the slots, they arecompletely covered by the side faces of the rotor. This prevents gasfrom blowing back through the slot to the trailing, lower pressurepocket. Thus the only blow-back that can occur is over the tip of thevane in the outlet zone (inherent in all sliding vane compressors) andsome small carryover of high pressure gas from the pockets in the rotorside faces.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of arotary gas compressor having an improved gas discharge arrangement;

FIG. 2 is a cross-sectional view taken along the plane of line 2-2 ofFIG. 1;

FIG. 3 is a cross-sectional view taken along the plane of line 33 ofFIG. 1; and

FIG. 4 is a cross-sectional view taken along the plane of line 44 ofFIG. I, but with the valve stop removed.

BRIEF DESCRIPTION OF THE INVENTION Referring to FIGS. 1 and 2, the gascompressor comprises a rotor assembly 11 rotatable within a statorassembly 12 and which serves as a housing for the rotor assembly. Moreparticularly, the stator assembly 12 comprises a cylinder housing '13and end plates 14 and held in engagement with housing 13 by bolts 16.The plates 14 and 15 are bored as at 17 and 18 to provide bearings forrotatably mounting the rotor assembly 11 within the stator assembly 12.

The rotor assembly 11 comprises a cylindrical rotor 19 having aplurality of equidistantly-spaced slots 20 receiving vanes 21 slidablyreciprocable therein. Rotor 19 is keyed at 22 to a drive shaft 23journalled in the bearings 17 and 18 and is adapted to be driven by apulley 24 connected to a motor (not shown) or other suitable drivemeans. In the case of an automotive application, the compressor isusually driven from the engine through an accessory drive system.

As shown in FIG. 1, the substantially cylindrical inner surface 25 ofthe cylinder housing 13 has a contact area 26 engaging the outercylindrical surface 19b of the rotor. Since the rotor is rotatablymounted on an axis 27 offset from the center line of the cylinder wall,the rotor is substantially in sliding contact with the contact area 26,leaving a generally crescent-shaped working chamber 28 extending over asubstantial portion of the inner periphery of the cylinder housing '13.

As best shown in FIGS. 1 and 4, a suction port 29 and a dischargepassage 30 are provided in the cylinder housing 13, both of whichcommunicate with the working chamber 28. A discharge gas plenum islocated between discharge passage 30 and a series of ports 41 whichcommunicate directly with the discharge gas zone 42 adjacent the contactarea 26. Ports 4] are drilled through a valve plate 43 to which issecured a valve 44 and valve stop 45 in a conventional manner. Forclarity, the valve stop is not shown in FIG. 4. Valve 44 is biased to aclosed position and requires a predetermined opening force to build upin the discharge zone 42 before gas may flow into plenum 40 anddischarge passage 30.

The improved gas discharge system comprises a plurality of substantiallyarcuate gas discharge slots 31 and 32 in the end faces of the housingplates 14 and 15, respectively, the slots communicating with dischargepassage 30 in the cylinder housing through the valve 44. The end faces19a and 19b of rotor 19 are provided with circumferentially-spaced fluidpassages 33, 34 lo cated on opposite faces 19a and 19b of the rotorimmediately ahead of each vane 21, in terms of the direction of rotationshown by the arrow, FIG. 1. The passages 33 and 34 cooperate with theslots 31 and 32 in a manner that the respective sets of the passages 33and 34 are successively placed in communication with the slots 31 and 32in the end plates 14 and 15 during rotation of the rotor in thedirection indicated by the arrow in FIG. 1.

In the operation of the compressor, the discharge slots 31 and 32 in thehousing plates 14 and 15 are effective to provide an alternate, lowresistance path for gas flow at a point located a substantial distancefrom the outlet port of the stator housing. As shown in FIG. 1, thepassage 33, which would be located directly across from passage 34, asillustrated, is just beginning communication with the entrance end 3112of slot 31. It will be noted that the passage is defined by the slot 31and the side face 19a of rotor 19 as the vane sweeps along. Accordingly,the gas may not flow back to the trailing pocket, as would be case ifthe slot 31 were located radially outwardly of the peripheral surface191; of rotor 19.

At the same time, gas may also be discharged through the primary passagedefined between the cylindrical surface 19b of rotor 19, end plates 14and 15, and surface 25 of the cylinder, as in a conventional rotarysliding vane compressor. It will be apparent from the foregoingdescription that there is provided an improved arrangement fordischarging high pressure gas from a compressor which effectivelyreduces the extremely high pressures normally generated in the outletarea as the vanes approach the same. The system also provides minimumflow resistance by avoidance of flow restriction to thereby insureproper compression at the outlet of the compressor.

What is claimed is:

1. A rotary gas compressor comprising a housing having a substantiallycylindrical interior surface and opposed end plates defining a closedchamber;

a rotor having a cylindrical peripheral surface and opposed side faces,said rotor being mounted in said chamber and rotatable about an axiswhich is offset with respect to the axis of said cylindrical interiorsurface, said rotor and said housing defining a generally crescentshaped compression cavity;

a gas inlet port and a gas discharge port communicating with saidcompression cavity;

a valve associated with said gas discharge port;

a plurality of vanes slidably supported in said rotor and engaging saidcylindrical interior surface;

means defining an elongated slot in at least one of said end plateshaving an exit end located in communication with said discharge port andan entrance end located at a point circumferentially spaced in adirection toward said inlet port and inwardly spaced from saidcylindrical peripheral surface, the entire slot being substantiallycovered by one of the side faces of said rotor; and

means defining a passage immediately adjacent each vane in said onerotor end surface extending away from the cylindrical surface andproviding a first flow path for gas which intermittently connects thatportion of the compression cavity ahead of the vane with the entranceend of said elongated slot, a second flow path, communicating with saiddischarge port, for gas being provided between the cylindrical surfaceon said rotor, the cylindrical inte rior surface of said housing andsaid end plates within said housing.

1. A rotary gas compressor comprising a housing having a substantiallycylindrical interior surface and opposed end plates defining a closedchamber; a rotor having a cylindrical peripheral surface and opposedside faces, said rotor being mounted in said chamber and rotatable aboutan axis which is offset with respect to the axis of said cylindricalinterior surface, said rotor and said housing defining a generallycrescent shaped compression cavity; a gas inlet port and a gas dischargeport communicating with said compression cavity; a valve associated withsaid gas discharge port; a plurality of vanes slidably supported in saidrotor and engaging said cylindrical interior surface; means defining anelongated slot in at least one of said end plates having an exit endlocated in communication with said discharge port and an entrance endlocated at a point circumferentially spaced in a direction toward saidinlet port and inwardly spaced from said cylindrical peripheral surface,the entire slot being substantially covered by one of the side faces ofsaid rotor; and means defining a passage immediately adjacent each vanein said one rotor end surface extending away from the cylindricalsurface and providing a first flow path for gas which intermittentlyconnects that portion of the compression cavity ahead of the vane withthe entrance end of said elongated slot, a second flow path,communicating with said discharge port, for gas being provided betweenthe cylindrical surface on said rotor, the cylindrical interior surfaceof said housing and said end plates within said housing.